svn commit: r350870 - stable/12/sys/dev/iicbus

[Ian Lepore]

Author: ian
Date: Sun Aug 11 21:21:32 2019
New Revision: 350870
URL: https://svnweb.freebsd.org/changeset/base/350870

Log:
  MFC r349839, r349850
  
  r349839:
  Call device_unbusy() on the error exit path, because if iicbus_request_bus()
  returns an error, iicbus_release_bus() is not going to be called.
  
  r349850:
  Restore the ability for i2c slave devices to do IO from their probe method.
  
  r348164 added code to iicbus_request_bus/iicbus_release_bus to automatically
  call device_busy()/device_unbusy() as part of aquiring exclusive use of the
  bus (so modules can't be unloaded while the bus is exclusively owned and/or
  IO is in progress).  That broke the ability to do i2c IO from a slave device
  probe method, because the slave isn't attached yet, so calling device_busy()
  triggers a sanity-check panic for trying to busy a non-attached device.
  
  Now we check whether the device status is < DS_ATTACHING, and if so we busy
  the iicbus rather than the slave device.  I think this leaves a small window
  where a module could be unloaded while probing is in progress.  But I think
  that's true of all devices, and probably should be fixed by introducing a
  DS_PROBING state for devices, and handling that at various points in the
  newbus code.

Modified:
  stable/12/sys/dev/iicbus/iicbus.h
  stable/12/sys/dev/iicbus/iiconf.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/dev/iicbus/iicbus.h
==============================================================================
--- stable/12/sys/dev/iicbus/iicbus.h	Sun Aug 11 21:15:30 2019	(r350869)
+++ stable/12/sys/dev/iicbus/iicbus.h	Sun Aug 11 21:21:32 2019	(r350870)
@@ -41,6 +41,7 @@ struct iicbus_softc
 {
 	device_t dev;		/* Myself */
 	device_t owner;		/* iicbus owner device structure */
+	device_t busydev;	/* iicbus_release_bus calls unbusy on this */
 	u_int owncount;		/* iicbus ownership nesting count */
 	u_char started;		/* address of the 'started' slave
 				 * 0 if no start condition succeeded */

Modified: stable/12/sys/dev/iicbus/iiconf.c
==============================================================================
--- stable/12/sys/dev/iicbus/iiconf.c	Sun Aug 11 21:15:30 2019	(r350869)
+++ stable/12/sys/dev/iicbus/iiconf.c	Sun Aug 11 21:21:32 2019	(r350870)
@@ -131,9 +131,15 @@ iicbus_request_bus(device_t bus, device_t dev, int how
 			/*
 			 * Mark the device busy while it owns the bus, to
 			 * prevent detaching the device, bus, or hardware
-			 * controller, until ownership is relinquished.
+			 * controller, until ownership is relinquished.  If the
+			 * device is doing IO from its probe method before
+			 * attaching, it cannot be busied; mark the bus busy.
 			 */
-			device_busy(dev);
+			if (device_get_state(dev) < DS_ATTACHING)
+				sc->busydev = bus;
+			else
+				sc->busydev = dev;
+			device_busy(sc->busydev);
 			/* 
 			 * Drop the lock around the call to the bus driver, it
 			 * should be allowed to sleep in the IIC_WAIT case.
@@ -150,6 +156,7 @@ iicbus_request_bus(device_t bus, device_t dev, int how
 				sc->owner = NULL;
 				sc->owncount = 0;
 				wakeup_one(sc);
+				device_unbusy(sc->busydev);
 			}
 		}
 	}
@@ -183,7 +190,7 @@ iicbus_release_bus(device_t bus, device_t dev)
 		IICBUS_LOCK(sc);
 		sc->owner = NULL;
 		wakeup_one(sc);
-		device_unbusy(dev);
+		device_unbusy(sc->busydev);
 	}
 	IICBUS_UNLOCK(sc);
 	return (0);